Automatic control systems may be used to control the functioning of various machines and devices. In operation, automatic control systems may output control signals causing motors of controlled devices to turn, valves to open, or circuit boards to power up. The control signals may be calculated by integrated circuits mounted on system boards.
However, the system boards of automatic control systems sometimes lack sufficient facilities for generating the control signals. For this reason, automatic control systems may use interface devices to generate and receive signals on their behalf. By using specialized circuitry, the interface devices may generate signals having a specified voltage, current, frequency, or another characteristic, which the automatic control systems cannot by themselves produce.